The use of snowthrowers (or snowblowers) by both commercial and residential operators is common for those located in snowy winter climates. Snowthrowers may be walk-behind units or may be propelled by other machinery (e.g., all-terrain vehicles, tractors, etc.). Typically, snowthrowers are divided into two categories: single-stage snowthrowers and multi-stage snowthrowers. Single-stage snowthrowers generally incorporate an impeller assembly that is driven by an internal combustion engine (or similar prime mover, such as an electric motor) to perform the functions of propelling the snowthrower forward, lifting snow from the surface to be cleared, and ejecting the snow out of a discharge chute. A multi-stage snowthrower includes a separate auger assembly and impeller assembly. Both the auger assembly and impeller assembly are driven by an internal combustion engine (or similar prime mover). The auger assembly rotates near the surface to be cleared in order to lift and direct snow and debris to the impeller assembly, which rotates along an axis perpendicular to the axis of rotation of the auger assembly. The impeller assembly then acts to eject snow out of a discharge chute.
In single-stage snowthrowers, the impeller assembly is generally formed of a flexible material which contacts the surface to be cleared as it is directed along a path by the user. Due to this direct contact with the surface, single-stage snowthrowers typically clear the entire surface of snow quite well. However, because the impeller assembly performs the tasks of propelling the snowthrower, lifting the snow, and ejecting the snow from the discharge chute, there are limitations to the size, shape, and material of the impeller assembly. These limitations reduce the effectiveness of the impeller assembly of a single-stage snowthrower in deep, icy, and/or heavy snow conditions.
On the other hand, multi-stage snowthrowers are generally more adept at clearing deep and/or heavy snow than their single-stage counterparts. This is because the auger assembly of multi-stage snowthrowers is typically formed of a rigid material (e.g., metal) that both separates and lifts the snow to be cleared and delivers it to the impeller assembly for ejection from the discharge chute. However, as the auger assembly is formed as a rigid component, the auger assembly is generally positioned within an auger housing so as to be a certain distance above the surface to be cleared. While in some ways it is advantageous for the rigid auger assembly to not contact the surface to be cleared, there is also the potential disadvantage of some snow being left behind and/or compacted as the snowthrower passes. Additionally, multi-stage snowthrowers are generally much larger, heavier, and more costly than single-stage snowthrowers.
Referring to FIG. 1 and FIG. 2, a conventional impeller and impeller housing assembly for a single-stage snowthrower is shown. While not illustrated, one of ordinary skill in the art would readily recognize that the impeller assembly 100 could be rotatably driven by any suitable prime mover (e.g., an internal combustion engine or electric motor). Assembly 100 includes an impeller 102 coupled to a driven shaft 104 which rotates about axis A within impeller housing 106. Impeller 102 operates to propel collected snow out of a discharge chute (not shown) of the snowthrower via flexible paddles 108a, 108b. Paddles 108a, 108b may be formed of any suitable flexible material, e.g. rubber. Each paddle 108a, 108b is coupled to driven shaft 104 via a central mounting plate 110 and respective side mounting plates 112a, 112b. As impeller assembly 100 rotates about axis A, paddles 108a, 108b contact the surface to be cleared of snow to not only lift and propel the snow out of a discharge chute, but also to propel the snowthrower in a forward direction of travel. However, as discussed above, due to the flexible nature and orientation of paddles 108a, 108b, icy or heavy snow is not readily broken down by impeller assembly 100, which may cause substantial clogging within the impeller housing and/or discharge chute.